Thirteen-lined ground squirrels have been known to hibernate for 250 days.

Eastern chipmunks stomp their feet and wave their tails to protect their territories.

Description and Identification

Three species of Illinois ground squirrels are described here. The fourth and largest "ground
squirrel," the woodchuck, is covered in a separate section. All ground squirrels are characterized by
a tail covered with hair, nesting in underground burrows, and internal cheek pouches. Most ground
squirrels hibernate and all four species are active during daylight hours. Ground squirrels avoid
burrowing in areas subject to flooding.

Eastern chipmunk (Tamias striatus): The eastern
chipmunk is the smallest Illinois ground squirrel at two to five ounces in weight and eight to 12
inches in total length. Eastern chipmunks have conspicuous light and dark stripes on the back, sides,
and cheeks. The fur on the upperparts is reddish-brown with rust color on rump and flanks. The belly
and sides are buff to white. The ears are rounded and erect. The tail is covered with fur but is not
bushy and is somewhat flattened. Chipmunks have internal cheek pouches that are used to transport food
or excavated soil. The chipmunk does not hibernate. Because they have limited digging ability, they
often "burrow" under rocks, logs, or buildings.

Thirteen-lined ground squirrel (Spermophilus
tridecemlineatus): The thirteen-lined ground squirrel is slender with large eyes and small
ears. They have yellowish fur and 13 prominent alternating light and dark stripes on the back and
sides. The light stripes are yellow to white, and the dark ones are black to reddish-brown with
lighter spots. The thirteen-lined ground squirrel hibernates in winter. In the fall before
hibernation, thirteen-lined ground squirrels weigh eight to nine ounces and are much larger than a
chipmunk. However, by spring when the squirrels come out of hibernation they weigh only four to five
ounces.

Franklin's ground squirrel (Spermophilus
franklinii): The Franklin's ground squirrel is a little larger than the thirteen-lined ground
squirrel, weighing one to one and a half pounds in the fall before hibernation. Franklin's ground
squirrels resemble gray squirrels but have a shorter, less bushy tail and smaller ears. They have
brownish-gray fur speckled with black and the underparts vary from yellowish-white to gray or buff.
The Franklin's ground squirrel is listed as a state threatened species in Illinois.

Habitat

The Franklin's and thirteen-lined ground squirrels are found in grasslands or prairies while the
eastern chipmunk lives in wooded areas. Eastern chipmunks prefer woodland borders rather than deep
forests, particularly sloped areas with woody underbrush. Thirteen-lined ground squirrels live in
short grasslands or in weedy areas with short vegetation. They are often found in golf courses,
cemeteries, parks, or roadsides. Franklin's ground squirrels are found in slightly taller grass, but
prefer the grass to be short enough to allow them to stand on their hind legs and see over the
grass.

Distribution and Abundance

Eastern chipmunks occur throughout Illinois where there is suitable habitat, although they appear
to be absent in the southeastern counties. Thirteen-lined and Franklin's ground squirrels occur in
the northern two-thirds of Illinois. The southern limit of these ground squirrels in Illinois seems to
correspond with the Shelbyville glacial moraine. Eastern chipmunks and thirteen-lined ground
squirrels are abundant in many areas of Illinois but Franklin's ground squirrels are uncommon and are
listed as a threatened species within the state.

Reproduction

Like tree squirrels, the eastern chipmunk has two breeding seasons, one in spring and the other in
late summer. Chipmunk gestation is 31 days with five to six young per litter. Chipmunks are weaned at
six weeks of age. Thirteen-lined and Franklin's ground squirrels have only one litter per year,
usually in late May. Gestation is 27 to 28 days with six to seven young per litter. The young are
weaned in about four weeks.

Behavior

Ground squirrels are diurnal meaning that they are active during the day. All squirrels are
solitary; however, since they are not territorial many may be seen in close proximity particularly if
there is a good supply of food at that location.

Damage Prevention and Control Measures

If ground squirrels are causing problems there are several control strategies available. Note:
Franklin's ground squirrels are threatened in Illinois and are protected. If you are having a problem
with Franklin's ground squirrels call your local IDNR District Wildlife
Biologist for assistance.

Habitat Modification

Encourage the growth of tall, herbaceous vegetation to deter
thirteen-lined ground squirrels from using the property.

Exclusion

Chipmunks should be excluded from buildings wherever possible.
Use hardware cloth with ¼ inch (0.6 cm) mesh, caulking,
or other appropriate materials to close openings where they could
gain entry. To keep ground squirrels from burrowing under foundations,
place hardware cloth bent at a 90° angle along the foundation
and cover with soil.

Repellents

There are currently no repellents registered for use against ground squirrels in Illinois.

Removal

If other control methods have failed, ground squirrels can be trapped and removed. A permit is not needed. Live-traps baited
with seed can be used to capture ground squirrels. If you plan to release the squirrel, it should be
released five to ten miles away. You will need permission of the landowner before you release the
squirrel. Rat-sized snap traps are efficient if ground squirrels are to be lethally removed.
Nuisance wildlife control operators will trap and remove squirrels for a fee.

Public Health Concerns

Ground squirrels in Illinois are not considered to be a public health concern. They can be carriers
of plague; however, transmission of plague from squirrels is extremely rare. There are only ten to
fifteen cases of plague reported in the United States each year, and most of these cases are from
western states. For more information about plague, read the Illinois Department of Public Health
Plague Factsheet.

Ecological Role

Ground squirrels play an important role in soil aeration. They help condition the soil for plant
growth. Their body wastes contribute to the organic structure of the soil. Ground squirrels are also
an important part of the food web, being preyed upon by several species of birds, mammals, and
snakes.

Legal Status

In Illinois, thirteen-lined ground squirrels and eastern chipmunks are not protected by the
Wildlife Code. The Franklin's ground squirrel is protected by the Illinois Endangered Species Act.